Fin patterning methods for increased process margin

A method of semiconductor device fabrication, comprising:

• forming a plurality of mandrels over a substrate and forming a pair of first spacers each having a first spacer width on sidewalls of each mandrel of the plurality of mandrels;
• etching the plurality of mandrels and forming a pair of second spacers each having a second spacer width on sidewalls of each first spacer;
• removing the first spacers and forming a pair of third spacers each having a third spacer width on sidewalls of each second spacer;
• and
• after forming the pair of third spacers, etching the second spacers and performing a first etch process to form fin regions within the substrate, wherein the third spacers mask portions of the substrate during the first etch process, and wherein a fin region width is substantially equal to about the third spacer width.

A method of fabricating a semiconductor device, comprising:

• fabricating mandrels over a substrate, wherein the mandrels define a pattern for subsequently formed first spacers;
• forming the first spacers on sidewalls of the mandrels, wherein the first spacers define a pattern for subsequently formed second spacers;
• removing the mandrels and forming second spacers on sidewalls of the first spacers;
• etching the first spacers and performing a second spacer cut process to remove a first set of second spacers and leave a second set of second spacers;
• forming third spacers on sidewalls of the second set of second spacers;
• etching the second set of second spacers and performing a third spacer cut process to remove a first set of third spacers and leave a second set of third spacers;
• and
• performing a substrate etch process to form fin regions within the substrate, wherein the second set of third spacers mask portions of the substrate during the substrate etch process.